1. Field of the Invention
The present invention relates to developer producing equipment and a developer producing method, and more particularly to equipment which is connected via piping to working equipment in which electronic circuits on which fine working is performed are formed, and which manufactures an alkali type developer that is used to develop photoresists or the like in the abovementioned working equipment, and a method for manufacturing this alkali type developer.
2. Description of the Related Art
Generally, resist materials used in photolithographic processes in the manufacture of devices such as electronic devices or the like that have electronic circuits on which fine working is performed include positive type materials that are solubilized by exposure to light, and negative type materials that are insolubilized by exposure to light. As one example, in the manufacture of semiconductor devices, flat panel display (FPD) substrates and the like, such photo-etching is repeatedly performed; accordingly, mainly positive type resists are commonly used.
Aqueous solutions of inorganic alkalies consisting of sodium phosphate, caustic soda, sodium silicate or mixtures of these substances with other inorganic alkalies or the like may be cited as examples of developer materials for positive type resists. Furthermore, in cases where contamination by alkali metals is a concern, aqueous solutions of amine type organic alkalies that contain no metals, aqueous solutions of tetramethylammonium hydroxide (TMAH), aqueous solutions of trimethylmonoethanolammonium hydroxide (choline) or the like are used. Among the latter materials, an aqueous solution of TMAH with a concentration of 2.38% are widely used.
Furthermore, developers prepared from these materials are used in large quantities in developing devices using a spray system, spin-coating system, dipping system or the like.
In developers used on photo-resists, the composition and concentration of the developer must be strictly controlled in order to obtain the maximum resolution, patterning sharpness (sharpness), stability and high yield in accordance with the developing process.
In particular, as the density of patterning has increased in recent years, there has been a demand for finer patterning widths. For example, in the case of semiconductor substrates, a demand has appeared for line widths on the 0.1 xcexcm level; furthermore, in the case of flat panel display substrates, there is now a demand for line widths on the 1 xcexcm level, and in the case of multi-layer printed circuit boards, there is a demand for line widths on the 10 xcexcm level. Furthermore, there is now a demand for line widths of 1 xcexcm or less in order to incorporate semiconductor circuits into flat panel display substrates using low-temperature polycrystalline silicon TFT techniques.
Consequently, there is a strong demand for improved precision of developer concentrations in order to reduce the variation in the effective sensitivity of photo-resists. For example, a range of values that deviate from the specified concentration by xc2x1{fraction (1/1000)} or less is required as the control range of the developer concentration. Especially in the case of an aqueous solution of TMAH, a range of values that deviate from the specified concentration by xc2x1{fraction (1/2000)} or less (more concretely, 2.380xc2x10.001 wt %) is required.
Furthermore, in order to eliminate patterning defects, it is required that various developers contain extremely few particles, i.e., the content of particles with a size of 0.1 xcexcm or greater must be 10 or fewer particles per milliliter of developer.
In recent years, moreover, there has been a further increase in the amount of developer used as a result of increased size and increased mass production of substrates.
Thus, along with a sharp demand for improved precision in developer concentrations and demand for particle-free developers, there has been a strong demand for measures to facilitate mass production and reduce cost.
In the case of conventional techniques, however, adjustment of the composition and concentration of developers in manufacturing plants for semiconductor devices and the like has been extremely difficult, not only in terms of equipment and operating costs, but also from the standpoint of sufficient control the of the composition and concentration of the developers.
For these reasons, it has been unavoidable necessary in manufacturing plants for semiconductor devices and the like (hereafter referred to as the xe2x80x9cuse sidexe2x80x9d) to use developers whose composition and concentration have been adjusted exclusively by the developer makers (hereafter referred to as the xe2x80x9csupply sidexe2x80x9d).
In such cases, a method is used in which a developer stock solution that has been prepared with a specified composition is diluted with pure water on the supply side, the developer thus adjusted to a specified concentration is places in containers, and this adjusted developer is supplied to the use side.
In this case, the dilution factor of the developer stock solution varies according to the solution composition and stock solution concentration, the type of positive resist or the like that is the object of development, and the intended use. Ordinarily, the stock solution is diluted approximately 8 to 40 times. Accordingly, the amount of developer prepared on the supply side is greatly increased in accordance with the dilution factor, thus resulting in an increase in the work involved in preparing containers and filling containers for the shipping of the developer to the use side, and an increase in shipping costs. As a result, such expenses account for a considerable portion of the cost of the developer.
Furthermore, considerable time is required for shipping and storage until the developer prepared on the supply side can be used on the use side, and the developer deteriorates during this period.
Moreover, since developers tend to absorb carbon dioxide gas from the air, variations in concentration caused by the absorption of carbon dioxide gas occur during the dilution operation and during the storage of the diluted developer, even if a dilution apparatus is installed on the use side. This may also be cited as one of the reasons why the dilution of developers has not been performed on the use side in semiconductor device manufacturing plants or the like.
In order to solve these problems, a developer dilution apparatus comprising an agitating tank into which a photo-resist alkali type developer stock solution and pure water are introduced and subjected to forced agitation for a specified period of time, conductivity measuring means for extracting a portion of the mixed solution in the agitating tank, measuring the conductivity of this solution and then returning the solution of the agitating tank, control means for controlling either the photo-resist alkali type developer stock solution or pure water that is supplied to the agitating tank on the basis of the output signal from the conductivity measuring means, a storage tank into which the mixed solution from the agitating tank is introduced, and in which this mixed solution is stored, and nitrogen gas sealing means for sealing the agitating tank and storage tank with nitrogen gas, is disclosed in Japanese Patent No. 2751849. Furthermore, this apparatus makes it possible to prepare the developer on the use side by mixing the developer stock solution and pure water.
However, when the present inventors investigated the abovementioned conventional apparatus in detail in the light of requirements arising in the manufacture of electronic circuit boards for semiconductor devices and the like, which have become progressively finer and thinner, it became clear that the precision of the alkali concentration and the particle concentration in the developer obtained are not always satisfactory, and that there is a strong demand for improved quality in terms of high precision and particle-free solutions.
Accordingly, the present invention was devised in light of the abovementioned facts; it is an object of the present invention to provide purified developer producing equipment and a purified developer producing method which make it possible to produce a developer with a specified concentration quickly and with good precision from a developer stock solution on the use side, and which make it possible to control the composition and concentration of the developer thus produced with good precision.
In order to solve the abovementioned problems, the purified developer producing equipment of the present invention is equipment which is connected via piping to working equipment in which electronic circuits on which fine working is performed are formed, and which manufactures an alkali type developer that is used to develop photoresists or the like in the abovementioned working equipment, this purified developer producing equipment of the present invention comprising a preparation tank to which a developer stock solution and pure water are supplied, and in which an alkali type developer is prepared, first alkali concentration measuring means for measuring the alkali concentration of the alkali type developer in the preparation tank, liquid supply control means for controlling at least the amount of developer stock solution that is supplied to the preparation tank or the amount of pure water that is supplied to the preparation tank, or both, on the basis of the measured value obtained by the first alkali concentration measuring means, a leveling (concentration-evening) tank to which the alkali type developer from the preparation tank is supplied, and which evens out the alkali concentration of this alkali type developer, and liquid feed/liquid surface level control means for feeding the alkali type developer from the preparation tank into the leveling tank, and adjusting the liquid surface level of the alkali type developer in the preparation tank and the liquid surface level of the alkali type developer in the leveling tank.
In the developer producing equipment constructed in this manner, the developer stock solution is diluted with pure water in the preparation tank so that a diluted developer is prepared. In this case, the concentration of the alkali constituting the developer component in the preparation tank is actually measured, and the liquidity is adjusted by the liquid supply control means on the basis of this measurement so that the developer has the desired concentration. Accordingly, the concentration can be adjusted quickly and easily, and concentration control can be accomplished with good precision.
Furthermore, the alkali developer that is obtained in the preparation tank inevitably tends to have a slight error in the alkali concentration. Accordingly, in the present invention, the alkali developer in the preparation tank is fed into a leveling tank, and the alkali concentration is evened out in this leveling tank. As a result, the precision of the alkali concentration in the developer is greatly improved.
Furthermore, since the developer thus prepared with the desired concentration can be supplied to working equipment via piping, separate storage or shipping costs are eliminated. Moreover, if the developer preparation apparatus including the piping connected to the working equipment is constructed as a system that is substantially sealed off from the atmosphere, deterioration of the developer caused by the absorption of carbon dioxide gas and the like in the atmosphere by the developer can be suppressed.
Furthermore, in the present equipment, the respective liquid surface levels in the preparation tank and leveling tank can be adjusted to any desired levels by the liquid feed/liquid surface level control means. In this case, it is desirable that the liquid feed/liquid surface level control means be means which are such that the alkali type developer is naturally fed from the preparation tank to the leveling tank, with such means having a communicating pipe that is connected to the preparation tank and leveling tank. As a result, both liquid surface levels are adjusted to substantially the same level by the hydraulic pressure difference, and disturbance of the liquid flow and the admixture of foreign matter can be effectively suppressed in this case.
In concrete terms, it is desirable that the leveling tank be equipped with second alkali concentration measuring means for measuring the alkali concentration of the alkali type developer in the leveling tank.
More concretely, the leveling tank is equipped with an agitation mechanism that agitates the alkali type developer in the leveling tank.
Even more concretely, the leveling tank is equipped with a filtration mechanism that filters the alkali type developer in the leveling tank.
Furthermore, it is desirable that circulation feeding (feed-back) piping that feeds (refluxes) the alkali type developer in the leveling tank into the preparation tank be provided.
Moreover, it is desirable that a storage tank which is disposed between the leveling tank and the working equipment, and which stores the alkali type developer, be provided.
Furthermore, a system which has a plurality of preparation tanks is also useful.
Alternatively, the preparation tank and leveling tank may also be constructed as an integral unit.
In addition, it is ideal if wet nitrogen gas sealing means that seal the preparation tank and leveling tank with wet nitrogen gas are provided.
Even more preferably, solute gas removal means that remove the solute gas contained in the alkali type developer are provided.
Furthermore, it is even more useful if fine particle number measuring means that measure the number of fine particles contained in the alkali type developer in the state prior to the supply of the alkali type developer to the working equipment are provided.
It is especially desirable that the first alkali concentration measuring means consist of at least one of the following devices: namely, a conductivity meter, and ultrasonic concentration meter, a liquid density meter or an automatic titration device.
Similarly, it is desirable that the second alkali concentration measuring means consist of at least one of the following devices: namely, a conductivity meter, and ultrasonic concentration meter, a liquid density meter or an automatic titration device.
Furthermore, the purified developer producing method of the present invention is a method that produces an alkali type developer that is supplied via piping to a working process that forms electronic circuits on which fine working is performed, this producing method comprising the steps of preparing an alkali type developer by agitating a developer stock solution and pure water, measuring the alkali concentration of the alkali type developer, adjusting either the amount of developer stock solution that is supplied to the alkali type developer preparation step or the amount of pure water that is supplied to the alkali type developer preparation step, or both, on the basis of the measured value of the alkali concentration of the alkali type developer, evening out the concentration of the alkali type developer obtained in the alkali type developer preparation step, and adjusting the liquid surface level of the alkali type developer in the alkali type developer preparation step and the liquid surface level of the alkali type developer in the alkali type developer leveling step.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.